1. Field of the Invention
The present invention relates to an image processing system using a paper user interface, and particularly relates to an image processing system which is suitable for improving the recognition accuracy of special marks or patterns for detecting a job control sheet.
2. Discussion of the Related Art
An image processing system using a paper user interface is disclosed in U.S. Pat. No. 4,737,348. In this image processing system, a paper user interface acts as a user interface utilizing an image reading device such as an image scanner or the like. This is done by using a job control sheet provided with marks for informing machine operation and for indicating attributes of a job. The job control sheet further has a job control sheet detection mark printed on it so that the job control sheet can be distinguished from any other ordinary documents.
Conventionally, the job control sheet detection mark has been printed longitudinally or transversely on a job control sheet, as shown in FIG. 10. For example, when the job control sheet detection mark is a bar code in which the widths of the respective straight lines or the intervals (spaces portions) between the straight lines have information, the straight lines are printed longitudinally, transversely, or substantially longitudinally or transversely on the sheet.
As shown in FIG. 10, when bar code 60 is printed in a recording system such as a copying machine, a printer, a facsimile equipment, or the like, there is a possibility that a linear stain or noise is longitudinally or transversely generated because of a scar, or the like, on a photosensitive drum. The noise appears as straight line 61 parallel to the lines of bar code 60. In mark detection and recognition processing, after a plurality of sampling guide lines 62 are discriminated, the code information on lines 62 is sampled. The detection accuracy of code 60 is thus improved by obtaining plural pieces of sampling information as described above. If noise 61 is generated close or on the portion where mark 60 is to be printed, there is a high possibility that noise 61 will be judged to be a part of the constituent element of mark 60. A problem exists, therefore, in that the detection accuracy is reduced because an error due to noise 61 is generated every time and at substantially the same position in each code information on sampling guide lines 62.